Some window covering horizontal slat sets are provided in standard widths and are provided such that customers can have the ends trimmed to a smaller size to make a custom fit within a window opening. This system enables the manufacturers to provide a smaller number of standard sizes, along with the provision that six to eight inches can be trimmed from the outer dimensions of the slats, the portion extending beyond the lift cords.
Typically a purchaser will have the seller perform two cuts at the time of sale to keep bilateral symmetry of the window covering horizontal slat sets. The majority of the window covering horizontal slat sets which are provided for cutting have base slats, regular slats and head rail members which extend laterally beyond the lift cords as constant cross sectional members and which have the ability to be cut with even force. If the material of the base slat and head slat presented different cutting softness, and uneven cut would occur. Further, during the cutting process, the window covering horizontal slat sets are supported in a compacted position with the head rail and base slat brought together and collectively orienting the intermediate slats together to enable them to be cut simultaneously.
The cutting devices provided at the point of sale are typically circular saws mounted on a miter-box arrangement and are typically used for making other types of cuts to a wide variety of other products. The blades are typically carbide tipped for long wear and are expensive to replace, especially since the cutting expenses are cost centers, typically with no charge being made to cut purchased product. Many retailers do not change the blades often, the objective being to have a blade continue in service until it is so worn that cutting becomes difficult.
Even when the blades are perfectly new and in 100% proper working order, the cut produced is almost never a clean cut. Any cutting motion which has an angle which produces a force component normal and leading away from a main surface of the slat had a tendency to produce a slight rip of the material on the main surface of the slat if the compression of the main surface is not maintained.
This surface end “rip” does not always become apparent when the window covering horizontal slat sets are cut in their compressed state, re-boxed and handed to the customer. The customer typically only detects any ripped surface at the time the window covering horizontal slat sets are installed, and usually after significant work in mounting the support brackets closely within a window opening and mounting the window covering horizontal slat set within the support bracket and testing the installed window covering. The ripped surfaces are most pronounced when the slats are tilted and depending upon which main surface the blade departed.
As before, the newer the blade, the fewer the ripped surface interruptions. It is impractical to use a new blade for each window covering horizontal slat set to be cut, and even if this were done, the ripped surfaces would not be eliminated. The negative aspects of the creation of ripped surfaces increase as the slat covering is colored differently than the material from which the slat is made. The more severe the color difference, the more noticeable the ripped surface.
The imperfections which occur during cutting are even more disappointing for the customer as the product is usually not returnable once it has been cut to the user's specific dimensions. Re processing to “touch up” the rips or jagged surface interruptions would require the use of a paint or surface material which matches the paint or surface material on the slat. This is very impractical and costly and would erase the savings which occurred from the use of a window covering horizontal slat set which was both engineered for and amenable to cutting.
The problem of ripping is created due to a number of effects. A first effect could lie in the limitations of the cutting system of the retail outlet (which can vary widely). As before, the blade might form a cutting angle which was given to higher ripping rates. The cutting table might not have a good structure to compress the slats of the window covering horizontal slat sets. However, even where a good compressive structure is available, the compression of the complete window covering horizontal slat set, including head rail, base rail and slats, will invariable result in some ripping.
This second effect is due to the use of a ladder tape or ladder rope which is generally a series of vertical cords joined by thinner cords to form a support for the slats. Movement of the vertical cords slightly upward or downward with respect to each other is what causes the window covering horizontal slats to achieve an angle together. The main vertical cords lie outside the slats and when the slats are drawn together by pulling the main ladder cord, they cause no impediment to close fitting of the adjacent slats, even if a good cutting support for the window covering horizontal slat sets are available. The thinner cords which form slat supports extend between each of the slats adjacent the lift cord.
Although the cords which join the first and second vertical ladder cords is quite thin, having one extend between each slat in the set adds significant spreading distance and impedes the slats from close contact at their ends, where the cutting occurs. Further, cutting tables are configured to compress the whole window covering horizontal slat sets from top to bottom and do not provide additional force at the ends immediately at the areas which are to be cut. Any such system might also cause the slats to be cut unevenly where the top slat is swept down and the bottom slat is swept upwardly.
Other structures can interfere with the cutting step including kinked lift cords or portions of the two main vertical ladder cords which inadvertently slip in-between any two adjacent slats. Further, any holding device which is capable of high compression of the window covering horizontal slat sets, particularly at the ends will have a high probability of damaging the head rail. The head rail typically has thin vertical walls and cannot withstand significant compression vertically. Where the head rail material is made of plastic, polyurethane, polyvinyl chloride, nylon, fiber glass, metal, glass, carbon composite, polypropylene, Teflon or other soft material amenable to cutting, over-compression could cause head-rail damage.
Applying pressure selectively to the slats near their tip ends would create a general bowing effects where the top and bottom slats would be shorter than the slats in the middle, and would create rips in the slats as the pressure on each slat was selectively cut and released as it was cut. Applying anything to the slats which could pull off the paint is also not advisable and could pose a safety hazard and perhaps damage the window covering horizontal slat set.
What is needed is a device and method to prevent rips which occur during cutting. The device should enable control and a high degree of cutting consistency regardless of the cutting system employed, and even where a cutting blade is near the end of its service life and has high blade wear. The needed device and method should be utilizable easily, both by factory producers, retail outlets who typically perform the cutting, and by users who elect to cut the window covering horizontal slat sets at home, at the time of installation.
The needed device and method should produce an even cut, and will avoid harsh and excessive application of force to the ends of the slats. The ideal device and method should not only be amenable for introduction at the manufacturing plant, but also be amenable for use on window covering horizontal slat sets produced by others by either the retail outlets or by users at the time of cutting of their window covering horizontal slat sets for home installation.